Unimig KUMJRRW205MIG, Operating Manual

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Electrode Included Angle/Taper - DC Welding
Tungsten electrodes for DC welding should be ground longitudinally and concentrically with diamond wheels to a
specific included angle in conjunction with the tip/flat preparation. Different angles produce different arc shapes and
offer different weld penetration capabilities. In general, blunter electrodes that have a larger included angle provide
the following benefits:
• Last Longer
• Have better weld penetration
• Have a narrower arc shape
• Can handle more amperage without eroding.
Sharper electrodes with smaller included angle provide:
• Offer less arc weld
• Have a wider arc
• Have a more consistent arc
The included angle determines weld bead shape and size. Generally, as the included angle increases, penetration
increases and bead width decreases.
Tungsten Preparation
Always use
DIAMOND
wheels when grinding and cutting. While tungsten is a very hard material, the surface of a
diamond wheel is harder, and this makes for smooth grinding. Grinding without diamond wheels, such as aluminium
oxide wheels, can lead to jagged edges, imperfections, or poor surface finishes not visible to the eye that will contrib-
ute to weld inconsistency and weld defects.
Always ensure to grind the tungsten in a longitudinal direction on the grinding wheel. Tungsten electrodes are manu-
factured with the molecular structure of the grain running lengthwise and thus grinding crosswise is “grinding against
the grain.” If electrodes are ground crosswise, the electrons have to jump across the grinding marks and the arc can
start before the tip and wander. Grinding longitudinally with the grain, the electrons flow steadily and easily to the end
of the tungsten tip. The arc starts straight and remains narrow, concentrated, and stable.
grind longitudinal on the
grinding wheel
don’t grind across
the grinding whee
l
flat tip
2.5 times tungsten diameter
pointed tip
Electrode Tip/Flat
The shape of the tungsten electrode tip is an important process variable in precision arc welding. A good selection
of tip/flat size will balance the need for several advantages. The bigger the flat, the more likely arc wander will occur
and the more difficult it will be to arc start. However, increasing the flat to the maximum level that still allows arc start
and eliminates arc wonder will improve the weld penetration and increase the electrode life. Some welders still grind
electrodes to a sharp point, which makes arc starting easier. However, they risk decreased welding performance from
melting at the tip and the possibility of the point falling off into the weld pool.
flat spot diameter
included angle
Tungsten Diameter at Constant Included Current Range Current Range
Diameter the Tip - mm Angle - Degrees Amps Pulsed Amps
1.0mm .250 20 05 - 30 05 - 60
1.6mm .500 25 08 - 50 05 - 100
1.6mm .800 30 10 - 70 10 - 140
2.4mm .800 35 12 - 90 12 - 180
2.4mm 1.100 45 15 - 150 15 - 250
3.2mm 1.100 60 20 - 200 20 - 300
3.2mm 1.500 90 25 - 250 25 - 350